Apparatus for growing large silicon carbide single crystals

Abstract

An apparatus for growing single-polytype, single crystals of silicon carbide utilizing physical vapor transport as the crystal growth technique. The apparatus has a furnace which has a carbon crucible with walls that border and define a crucible cavity. A silicon carbide source material provided at a first location of the crucible cavity, and a monocrystalline silicon carbide seed is provided at a second location of the crucible cavity. A heat path is also provided in the furnace above the crucible cavity. The crucible has a stepped surface that extends into the crucible cavity. The stepped surface has a mounting portion upon which the seed crystal is mounted. The mounting portion of the stepped surface is bordered at one side by the crucible cavity and is bordered at an opposite side by the furnace heat path. The stepped surface also has a sidewall that is bordered at one side by and surrounds the furnace heat path. The apparatus may also have a thermal insulating member, in which a side of the stepped surface sidewall opposite to the furnace heat path is bordered by the thermal insulating member.

It is claimed: 
     
       1. An apparatus for growing single-polytype, single crystals of silicon carbide, wherein the crystal growth occurs by a physical vapor transport, said apparatus comprising: (a) a furnace having a carbon crucible with walls that border and define a cavity therein;   (b) a silicon carbide source material provided at a first location of the crucible cavity;   (c) a monocrystalline silicon carbide seed provided at a second location of the cavity; and   (d) a radiation heat leak heat path provided in the furnace proximate the second location of the crucible cavity.   
     
     
       2. The apparatus of claim 1 further comprising a stepped surface of said crucible extending into said crucible cavity, wherein said stepped surface has a mounting portion upon which said seed is mounted that is bordered at one side by the crucible cavity and is bordered at an opposite side by said furnace heat path, and wherein said stepped surface has a sidewall that is bordered at one side by and surrounds said furnace heat path. 
     
     
       3. The apparatus of claim 2 wherein a side of the stepped surface sidewall opposite to the furnace heat path is bordered by a thermal insulating member. 
     
     
       4. The apparatus of claim 3 wherein the insulating member is made of carbon. 
     
     
       5. The apparatus of claim 4 wherein the carbon insulating member is made of graphite. 
     
     
       6. The apparatus of claim 4 wherein the carbon insulating member is porous. 
     
     
       7. The apparatus of claim 4 wherein the carbon insulating member is a carbon felt. 
     
     
       8. The apparatus of claim 3 wherein the insulating member is made of a plurality of carbon shields. 
     
     
       9. The apparatus of claim 8 wherein the carbon shields are made of graphite. 
     
     
       10. The apparatus of claim 2 wherein the stepped surface sidewall has a thickness that is less than the thickness of the stepped surface mounting portion. 
     
     
       11. The apparatus of claim 10 wherein the stepped surface is composed of pyrolytic graphite oriented so as to increase the temperature of the sidewall relative to the mounting portion as heat flows through said stepped surface. 
     
     
       12. The apparatus of claim 2 wherein the stepped surface mounting portion has a surface facing the crucible cavity that has a smooth finish thereon. 
     
     
       13. The apparatus of claim 1 wherein the furnace heat path is an aperture in the furnace.